Background
Currently, most if not all headlamps are made with tungsten halogen capsules. The capsule is typically a glass or quartz tube that is press sealed. The capsule gets quite hot during operation, so the capsule is usually held by a metal retainer. Metal retainers commonly are either snap fitted around the press seal of the capsule, or formed from two pieces that are welded or crimped together to trap the press seal. The capsule end is then pinned by the surrounding metal retainer.
Metal retainers are not completely satisfactory. Since the retainer should not rust, or distort under prolonged exposure to heat, stainless steel is used, so cost of the metal is one problem. Each lamp capsule must be accurately located in the reflector and lens system, but forming metal accurately for each lamp requires expensive equipment, and constant monitoring. Metal is hard, and the metal retainer can apply great pressure to the lamp capsule, if the retainer is not formed accurately. A misformed metal retainer can close too closely on the glass or quartz capsule, causing the capsule to fracture or explode. Welding the metal pieces can also cause problems. Improper welds fail, releasing the metal pieces, allowing the lamp capsule to move from the ideal optical position of the lamp. Repositioning and rewelding the clamp then becomes a cost issue. There is then a need for a lamp holder that is not hard, welded or metal.
A metal retainer, in the case of an HID automotive headlamp, cannot be used to hold the capsule because of the high voltage needed to ignite the lamp. With a metal retainer, the ignition voltage may break down outside the lamp. If the voltage breaks down outside the lamp, the lamp does not ignite, which would be a general safety hazard for vehicle operation, and could be a personal safety issue for those working with the lamp. There is then a need for a nonconductive holder to support and insulate an HID lamp.